Limncea peregra nionst. slnistrorsiim, in Durham. 113 



engfineers are universally agreed that the Productive Coal- 

 measures contain few or no distinctive lithological characters 

 by means of which the position reached in a boring or experi- 

 mental shaft-sinking- may be recognised. These marine bands 

 appear to afford such a clue. To make this certain, it is 

 necessary that the persistence of the bands should be definitely 

 proved. This can only be done with the help of local geologists 

 who will take the trouble to carefully examine all railway 

 sections likely to intersect these horizons, and who will visit new 

 sinkings, and examine at frequent intervals the material 

 brought to the surface. In thus appealing to Yorkshire 

 geologists, 1 do so with the perfect confidence that this appeal 

 will not be in vain. Yorkshire geologists have examined the 

 Chalk Formation for themselves : they will not hesitate to zone, 

 even in a more systematic manner, their county's magnificent 

 development of Coal-measures. In so doing, the debt owing by 

 geologists to mining enterprise may be in part repaid ; while 

 the unique Fish fauna of the marine beds of the Coal-measures 

 holds out hopes that he who cares to seek may add a link more 

 to the well-forged chain of palaontological evolution. 



LIMN/EA PEREGRA MONST. 

 SIN/STRORSUM, IN DURHAM 



C. T. TRECHMANN, B.Sc. 



Having read of the occurrence of this interesting monstrosity 

 in North Leeds (' Naturalist,' July 1901), I should like to record 

 the finding of this mollusc near Hesleden, Co. Durham. 



The locality is a small pond, quite near the vicarage, where 

 they were first noticed more than thirty years ago, as my 

 grandfather informs me, by the late Canon Tristram, then rector 

 of Castle Eden. Since then they were unnoticed till about 1895 

 when I obtained a few specimens while dredging for newts. 

 I have repeatedly searched the pond since 1899 and have seen 

 it practically trampled dry by cattle in the summer time, but 

 it was not till July 1903 that I found them again ; minute 

 specimens crawling up the grass stalks in one end of the 

 pond. Further searching resulted in the acquisition of quite 

 a number, all about the size of a pin's head. They were 

 put in an aquarium where they grew rapidly and spawned 

 profusely during the spring and summer of 1904 and 1905. 



1906 April I. 



